BBC - bbc.co.uk homepage - Home of the BBC on the Internet has good materials. BBC is a good model, highly respected, and careful in how they use English.
Note that there is more than one British accent.
Except for "r", which in English is really a semivowel, the consonants don't change much between British and North American English. The differences are mainly in vocabulary, idioms, and sometimes, the vowels.
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